opposite top This pile of raked leaves can be used directly to cover the ground, conserve moisture, and suppress weeds in areas without vegetation or in areas where the vegetation is tolerant of a degree of leaf cover. Opposite eottoMm This “mitten mulch” was produced without human effort by a small grove of sassafras (Sassafras albidum). vor tery A leaf-covered ground layer in between a planting of Christmas ferns (Polystichum acrostichoides), asters, and shrubs contributes to the moist conditions necessary to sustain an American toad (Bufo americanus). Toe nicuy Acardinal forages for seeds and insects in February in-between ferns in a garden. The bird wouldn't be here if the ground was covered in uniform turf or if the natural organic accumulation on the surface had been removed in favor of sterilized commercial mulch. Apove These bluejays aren’t waiting fora meal at the table in this December photo. They're foraging for acorns that have fallen from the large oak tree overhead. Thc pe Ine Ground Layer
RIGHT Newly germinated seedlings of American beech (Fagus grandifolia) appear under beeches in our garden. Seedlings at this stage are easily transplanted. CENTER These Oriental bittersweet (Celastrus orbiculatus) and Japanese honeysuckle (Lonicera japonica) seedlings established quickly on disturbed open ground. Removing any unwanted plants is easiest while they are still young. BELOW Mosses established themselves in the interstices of this dry-laid stone patio on the north side of our house, which is never irrigated. Knowing that mosses are an ideal substrate for germinating bluets (Houstonia caerulea), we scattered seeds and now enjoy blooming bluets each year from late March to early May. Weeds and Seedlings A ground layer covered in leaves provide ic eal The ability to spot ee seat required to eliminate mature plants. — Moss when in bloom. —RD LEFT What child isn’t captivated by a hover fly, here resting momentarily ona bluet? Also called flower flies or syrphids, these non-stinging, non-biting insects belong to the insect family Syrphidae. They ward off predators conditions for the coe and Brow able oe at ca) ee is an importa be Hout of as addition by reduction. Similarly, the ae dee With no sacrifice WBN CHON: ava se plants, which in turn are visited by insec 7 by mimicking the colors and patterns of bees and wasps. Adults subsist _ principally on nectar and pollen. As adults, syrphids pollinate many types of flowers, but as — larvae, they are efficient - predators of aphids.
The mossy ground layer of art gallery owner John Cram’s North Carolina garden is an ideal foil for sculpture and the sculptural forms of old trees and stone benches. The Ground Layer 149
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THE HERBACEOUS LAYER The potential botanical diversity of a garden’s herbaceous layer is much greater than that of any other aboveground layers—there simply are more species of herbaceous plants than of woody plants. Designing for high biodiversity in the herbaceous layer can benefit both humans and wildlife. Greater diversity results in more color, texture, form, fragrance, and seasonal interest pleasing to gardeners. It also increases the likelihood of determining which species really are best adapted to site conditions. From the perspective of wildlife, a more diverse herbaceous layer provides more varied shelter and cover. An overlapping sequence of bloom throughout the season translates toa continual source of nectar and pollen along with a steady supply of ripening seeds and fruits. If diversity is sufficient to ensure that multiple plants are capable of fulfilling each of these vital functions at any one time, this “system LEFT An herbaceous layer consisting primarily of ostrich fern (Matteuccia struthiopteris var. pensylvanica), wild ginger (Asarum canadense), and fernleaf phacelia (Phacelia bipinnatifida) covers a large area at Mt. Cuba Center in Delaware in late April, with occasional wood poppies (Stylophorum diphyllum) adding to the mix. All of these plants are adapted to the site conditions, and their rates of growth and spread are well enough balanced that this planting can be maintained indefinitely with minimal intervention by gardeners. RIGHT Also at Mt. Cuba Center, the herbaceous layer in this area is more diverse on a per-square-yard basis, with complex intermingling of interrupted fern (Osmunda claytoniana), trillium (Trillium flexipes), Virginia bluebells (Mertensia virginica), and wood poppy (Stylophorum diphyllum). Managing this composition requires more effort than the previous image, but because the group dynamic is fairly balanced, the maintenance isn’t excessive. redundancy” becomes a hedge against gaps or complete failures. One potential down side of plant diversity in gardens is that it is often concentrated at too small a scale. For the love of plants, gardeners sometimes group too many species with distinctly different growing needs into areas that are too small or not diverse enough to sustain them. The usual results are plantings that are difficult or impossible to maintain in the long run. Looking to healthy natural habitats as models is a reminder that while the overall plant diversity of a landscape may be high, in any given space or localized ecosystem there is considerable repetition of a few key species. When designing for diversity, it’s important to aim for the highest supportable biodiversity overall but to avoid unsustainable variety in any one spot. Developing a working knowledge of the dynamics of mixed plantings—the relative The Herbaceous Layer 151
This juxtaposition of creeping phlox (Phlox stolonifera), eastern foamflower (Tiarella cordifolia), and mayapple (Podophyllum peltatum) makes an attractive photograph, but maintaining this composition in the landscape is a high-maintenance proposition. The phlox spreads strongly enough that it will overrun the foamflower from one direction and the mayapples will overrun it from the other. While plantings like this may be maintainable ona small scale, they are not practical for creating a durable, low-maintenance herbaceous layer over larger areas. growth rates and abilities of plants to spread or resist spreading neighbors—is also necessary to efficiently managing diversity. Maintenance strategies greatly influence the effective functioning of any amount of plant diversity. For example, cutting a plant back prematurely in the interest of neatness may shorten its lifespan or reduce its capacity to suppress weeds sprouting around it. It may eliminate seed production or dispersal and, with this, the plant’s ability to perpetuate itself. It is also likely to reduce the food, cover, and shelter value to wildlife. Biennials comprise a highly functional group of herbaceous plants that are often overlooked because their life cycles are less familiar than those of annuals or perennials. After germinating, a biennial produces only vegetative growth in the first growing season. It flowers the second year, then dies after producing seed. Within a population of biennials there will always be first-year plants and second-year plants, meaning that there will almost always be foliage present (except in winter) and there will be flowering plants each year. 152 Applying Layers to the Home Garden Though annuals and biennials should not be discounted, perennial species comprise the majority of herbaceous plants suitable for residential landscapes. The word perennial suggests a capacity to live indefinitely; however, the likelihood of this is entirely dependent upon how well a plant is matched to site conditions. Though much can be done to improve the soil and growing conditions on a residential property such as adding organic material, changing the grade, improving drainage, or in extreme cases replacing the soil, the most conserving approach is to begin with a realistic assessment of existing conditions and to look for plants capable of thriving with a minimal amount of intervention. Balance and Durability in Diversity The herbaceous layer provides a wealth of habitat niches that vary in structure and composition and provide cover, shelter, and sustenance for a hugely diverse population of invertebrates. Among the many that live amid the herbaceous and ground layers, click beetles are important detritivores—they eat organic detritus. There are nearly 1000 click beetle species in North America, and most play important roles in breaking down coarse woody debris. They are best known to humans by their escape mechanism. A spine on the ventral surface of their first thoracic segment hooks into a notch on the second segment. Applied muscular pressure causes the spine to snap loose with a loud click, flinging the beetle several times its body length out of harm’s way. Many other fascinating creatures are supported by the herbaceous layer. When pairing or mixing herbaceous plants in a planting, it is important to consider their individual growth rates and, ideally, to select species with similar rates. Asters and heucheras, for example, are commonly used together in gardens. If white wood aster (Aster divaricatus) is paired with American heuchera (Heuchera
LEFT Aromatic aster (Aster oblongifolius) and large-rooted heuchera (Heuchera macrorhiza) are both relatively large, strong-growing, long-lived plants that are well matched against each other. This fall-blooming heuchera species is asoutheastern North American native that is sun and heat tolerant. It is semi-evergreen except in far northern locations. Botanists sometimes include it in H. villosa, but that species lacks the large woody rhizomes of H. macrorhiza. The commercial name Autumn Bride refers to H. macrorhiza. ABOVE Aclick beetle about ABOVE RIGHT Americanheu- _ aster (Aster divaricatus). to fly uses a foamflower chera (Heuchera americana) Maintaining a mix of the stalk as a take-off point. is a relatively long-lived two will require occaclump-former, but it is not sionally pulling the aster as strong as white wood away from the heuchera. The Herbaceous Layer 153
Both woodla phlox (Phlox divaricata) (above) and creeping phlox (Phlox stolonifera) (right) are durable spreaders. 54 Applying Layers to the Home Garden
americana), however, the aster will overrun the heuchera. For a balanced pairing, try aromatic aster (A. oblongifolius) and large-rooted heuchera (H. macrorhiza). They make a reliable combination for covering large areas in sun, and the heuchera can also be planted in shade. The key to a durable herbaceous layer is to rely primarily on a mix of clump-forming plants that are inherently long-lived, plants that regularly perpetuate themselves by self-sowing, and spreading plants that have a capacity for self-repair. Phloxes meet these criteria. Maintenance Strategies Though herbaceous plants are commonly selected for their ornamental flowers, they often contribute other necessary qualities in the landscape. A disproportionate focus on species with showy flowers has long obscured the functionality of plants such as barren strawberry (Waldsteinia lobata). Despite its small flowers, this southeastern native produces a dense mat of shiny green leaves in even tough sites and requires little maintenance in the process. It has high functional value in the biodiverse garden. Herbaceous plants with low maintenance requirements are especially attractive to today’s busy gardeners. Plants don’t have to look tough to be durable, as delicate-looking maidenhair fern (Adiantum pedatum) and Virginia bluebells (Mertensia virginica) demonstrate. When grown RS Meta aN Top Low-growing cold-hardy barren strawberry (Waldsteinia lobata) has insignificant yellow flowers, but the evergreen foliage makes it an ideal ground cover in shade or part sun. LEFT A delicate new frond of maidenhair fern (Adiantum pedatum) unfurls in early May. Oh a hate yi The fern’s refined appearance belies its long-lived nature. ABOVE A shade-tolerant mix of maidenhair fern, woodland stonecrop (Sedum ternatum), and zigzag goldenrod (Solidago flexicaulis) has a good dynamic balance and can be maintained with little effort. The Herbaceous Layer 155
within a ground-covering layers of other plants, the fern can persist indefinitely, and the bluebells, for decades. The natural cycle of Virginia bluebells and most native spring ephemerals makes them well suited to provide early bloom in areas of the garden that are very dry later in the season. Summer drought is no threat to these plants because they are dormant by that time. However, because they can leave a “hole” in the herbaceous layer when they go dormant, spring ephemerals are often ignored by gardeners. The answer is a mixed planting in which ephemerals are interspersed with plants that have a presence through the growing season. In early April the foliage tichum acrostichoides) and flower buds of Vir- (above left). Among the ginia bluebells (Mertensia earliest blooming spring virginica) push up through ephemerals, Virginia blueevergreen layers ofwood- _ bells provide essential land stonecrop (Sedum pollen and nectar services ternatum) (above) and at the very beginning of Christmas fern (Polys- the growing season (top). 156 Applying Layers to the Home Garden
ee iy Roots of river birches (Betula nigra) planted a quarter century ago make competition for moisture in summer a Serious issue in this area off a walkway in our Pennsylvania garden. Despite this, an herbaceous layer consisting of woodland stonecrop, Christmas ferns, white wood aster (Aster divaricatus), Virginia bluebells, and three non-native species—snowdrops (Galanthus nivalis), epimedium (Epimedium pinnatum subsp. colchicum), and wood tulip (Tulipa sylvestris)—thrives without irrigation and with minimal refereeing on our part. —RD The Herbaceous Layer 157
Mayapples (Podophyllum peltatum) cover a large partly shaded area in our garden in mid-April (above). There's little in the herbaceous plant palette anywhere in the world that can provide this much textural drama with so little effort. We've integrated woodland stonecrop, white wood aster, woodland geranium (Geranium maculatum), and various evergreen ferns including Christmas fern into the mix, so the ground remains vegetated after the mayapples subside (right). —RD 158 Applying Layers to the Home Garden
Weed Suppression Fernleaf phacelia (Phacelia bipinnatifida) is a biennial that produces showy lavender-blue blossoms in April and May, which in turn provide copious quantities of nectar and pollen for native bees and other hymenopterans. It selfsows readily, but can easily be kept in bounds by grubbing out any excess plants when young. It has the capacity to establish itself in highly shaded conditions below.and between shrubs and trees, and the low foliage of first-year plants makes an effective drought-tolerant weed-suppressing ground cover. Like fernleaf phacelia, Virginia waterleaf (Hydrophyllum virginianum) is also in the waterleaf family (Hydrophyllaceae). The family name refers to the light gray-green markings on mature leaves that resemble water marks. Virginia waterleaf is a deciduous perennial with attractive but relatively small white spring flowers. It creates a 4- to 6-inch tall mat of foliage that beautifully covers the ground for the remainder of the growing season. It is easily grown in part sun or dense shade. Though it is dense enough to have real weed-suppressing value, the foliage and root system are delicate enough that other perennials can persist within it. Virginia waterleaf creates a nomaintenance groundcover under native azaleas, as new leaves of pinkroot (Spigelia marilandica) and maidenhair fern (Adiantum pedatum) begin to emerge and anon-native bluebell (Hyacinthoides hispanica). oF The Herbaceous Layer
ABOVE In April, fernleaf phacelia fills the shady spaces behind a bench at Mt. Cuba Center with a carpet of lavender-blue flowers. RIGHT Foliage of first-year plants of fernleaf phacelia makes an attractive shade- and drought-tolerant ground cover. 160 Applying Layers to the Home Garden
Wildlife Support Strongly running species such as mountain mint (Pycnanthemum muticum) are often avoided when selecting plants for the herbaceous layer; however, in the right place and for the right purpose these plants can be the ideal choice, Mountain mint, for example, is a food source for butterflies, bees, and wasps in midsummer and can provide a durable presence through changing light conditions ina garden, —RD We planted mountain mint around the interior margin of a circular space in our garden that will in the long term be defined primarily by trees and shrubs. The mint proved adaptable enough to tolerate the initial full sun conditions (above), yet has persisted even as conditions have become increasingly shady (left). Herbaceous species that can survive such transitions are an important part of the functional palette. tor Mountain mint attracts large numbers of tiger swallowtails in late July (left). The nectar also attracts the blue winged wasp (Scolia dubia) (right). Like most ground-nesting solitary wasps, this species is docile and does not attack humans. It is a useful predator of the grubs of Japanese beetles.
RIGHT Common blue violet makes an attractive flowering groundcover. BELOW Aselfsowing, selfperpetuating population of naturalized violets serves as a deciduous ground cover under large trees while providing plenty of material for fritillary larvae to eat. The violets are easily kept in check by mowing along the edge were they meet the turf. Plants such as the common blue violet (Viola sororia), long dismissed by gardeners as a weed, can be reconstituted as desirable components of the herbaceous layer when their ecosystem functionality is re-evaluated. Violets are the sole larval food source for fritillary butterflies. Eliminating violets eliminates fritillaries, but finding ways to incorporate violets in garden design supports fritillaries. With proper plant selection and management, a diverse herbaceous layer can provide beauty and ecosystem services for all late into the season. Plants in the aster family (Asteraceae) are among the latest blooming, and most provide edible seeds throughout winter if allowed to stand.
The striped cream violet (Viola striata) has proved an easily ~~ managed choice - for the edge of this layered planting. ‘that includes white wood asters, wood geraniums, shrubs, and trees. ABOVE A New England aster RIGHT A bee and monarch (Aster novae-angliae) provides butterfly share a heartnectar toafemaletawny-edged _ leafed aster (Aster cordiskipper in mid-September. folius) in early October. The Herbaceous Layer 163
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166 Applying Layers to the Home Garden Th c j e€ ECOIOg sical Functiona lity of Hy lybri ids A ee question prompted by hybrids and cultivated varieties of natives produced by selection is “Do they still function as natives?” In most cases, if hybridization has not changed the chemical makeup in ways that make it unpalatable to native insects, the plant will still function as a native in this regard. If hybridization or selection hasn’t changed the physical form or structure of reproductive parts in ways that make them inoperative, then the hybrid is likely to function much like an unmodified plant. In some cases, hybridization or selection of native species produces garden plants that bloom at times that are out of sync with typical forms of the species. This may result in plants that are no longer contributors to the development of local gene pools and/or plants that are not providing ecosystem services such as pollen, nectar, or seeds at times when they are needed by local fauna. Hybridity and selection can also positively or negatively affect adaptability and longevity, both of which are important qualities to consider when designing sustainable layers. Sanguinaria canadensis ‘Multiplex’ is a cultivated variety of acommon native species. Instead of functioning reproductive parts, it has additional petals. Because of this, ‘Multiplex’ is sterile—it is incapable of producing seed. If you're an ant looking for eliasome-appendaged seeds, you're out of luck. But does this mean the double bloodroot has no function? Of course not. It functions as a beautiful element in the garden and that has value. It also still has all TOP LEFT A variegated cultivated varieties fritillary takes nectar derived from a comfroma patented hybrid mon native species. coneflower, Echinacea ‘Tomato Soup’. LEFT Functioning reproductive organs CENTER Double bloodroot are at the center of a (Sanguinaria canadensis typical bloodroot flower ‘Multiplex’) is surely and enable the species one of the most elegant to perpetuate itself.
the adaptability of the typical form of the species except that it is unable to perpetuate itself. As long as the garden as a whole is comprised of functional layers, there is no reason not to include a measure of single-function elements. To ensure that even longlived species such as Jack-in-the-pulpit (Arisaema triphyllum) remain part of the herbaceous layer, itis best to allow seeds to mature, be dispersed, and germinate.
Providing fragrance is a function of plants and gardens that is important to human sensibilities, and good design will make the most of this potential. to the Home Garden The sweet fragrance of strategically placed summer phlox (Phlox paniculata), a native of eastern United States, is readily accessible in this July image. Natives in Formal and Informal Designs Though native plants are sometimes considered appropriate only for informal design styles, there’s no reason for this. Style, and formality or informality, have more to do with management than with plant selection. Ferns are among the most adaptable and durable possibilities for the herbaceous layer. Though many are deciduous, a few including marginal shield fern (Dryopteris marginalis) and Christmas fern (Polystichum acrostichoides) are fully evergreen. Two running species, hayscented fern (Dennstaedtia punctilobula) and New York fern (Thelypteris noveboracensis), can be used to create highly durable herbaceous layers at a large or a relatively small scale. Ferns come about as close to being immune to deer damage as any group of native plants in eastern North America.
seit ad ip {Seay a. ee vs phe PU aie F 7) ira: OPPOSITE BOTTOM The vegetation edging this bluestone walk is mostly white wood aster (Aster divaricatus). A quick trimming with hand shears twice over the course of the growing season keeps this native aster looking neat enough for most eyes. LEFT Native mayapples dominate the spring herbaceous layer on a wooded slope above an outdoor dining area at Patterns, the private residence of Governor and Mrs. Pierre S. du Pont in Delaware. Patterns includes an inspired mix of informal and highly formal plantings. ABOVE In this lateNovember image, Christmas ferns function as an evergreen edge defining a woodland path. The Herbaceous Layer 169
In lieu of lawn, sunlit sweeps of hayscented fern (Dennstaedtia punctilobula) and New York fern (Thelypteris noveboracensis) cover the landscape in front of Russ Jones’ historic Pennsylvania cabin.
Managed Wildness Pinkroot or spigelia (Spigelia marilandica) is an excellent example of a showy, highly desirable native perennial that is difficult to propagate commercially but is easily naturalized in the garden. Though spigelia can be rooted from cuttings, the success rate is typically low. It grows easily from seed, but is explosively dehiscent: as the seed capsules ripen, they propel the seeds far from the plants, making seed collection problematic ina production setting. The species is a member of the logania family (Loganiaceae), which is closely related to the gentian family (Gentianaceae). The relationship can be observed in the opposite leaves and tubular flowers shared by spigelia and many gentians. Spigelia’s native range is concentrated in the southeastern states. Although garden literature typically says it grows only in moist woods and along stream banks, I've seen it growing wild in Tennessee at the bottom of a dry sunny slope below a shrub layer dominated by fragrant sumac (Rhus aromatica) and with American smoketree (Cotinus obovatus) growing above. Having grown it personally for over a quarter century | can say with confiderice that it is easily adaptable to garden soils of average moisture and to sites exposed toa significant amount of filtered sunlight. | wouldn't call it a weed, but we get hundreds of spigelia seedlings each year from the naturalized populations in our Pennsylvania garden. None of them were deliberately planted—they are all self-sown. Decades earlier when | first bought the property, | obtained Spigelia marilandica from three different growers whose thorough records traced the origin of their plants to different wild populations in North Carolina and Tennessee. This genetic diversity may be responsible for the vigor of the populations in our garden, but in any case, we allow spigelia to tell us where it would like to grow, It has become a reliable presence in a number of areas, blooming in June and often re-blooming BELOW EEL EHune dreds of self-sown plants of pinkroot bloom among shield ferns and cinnamon ferns in late June. later in summer. Whenever it gets too rambunctious, we dig up the seedlings and give them to gardening friends. Managed wildness and an invitational approach to chance happenings can sometimes accomplish things that would be impossible BELOW The tubular flowers of spigelia betray its affinity with gentians. through more deliberate methods. —RD The Herbaceous Layer 171
i hat ae Se Spigelia makes up a significant part of the herbaceous layer in this sitting area in the Darke-Zoehrer garden, where it mingles with white wood aster (Aster divaricatus), showy trillium (Trillium grandiflorum), Virginia waterleaf (Hydrophyllum virginianum), zigzag goldenrod (Solidago flexicaulis), maidenhair ferns (Adiantum pedatum), and many others. Spigelia is a reliable presence in the garden, blooming in spring and often reblooming in summer.
A Window on Diverse Functionality This following series of images illustrates the experiences—our “necessary journeys” to quote transformation of a relatively sterile space off a Ralph Waldo Emerson. Bringing life into these litnorth-facing bathroom window of our Pennsyl- tle landscapes can add immeasurably to the joy, vania home. Though a bathroom view may seem the intrigue, and the functionality of the garden as mundane, like the view from a kitchen window inclusive habitat. —RD it is asmall but significant element in our daily Installed by the original owners 40 years \ earlier as “foundation plantings,” these Japanese yews may have provided some cover for wildlife, but their contributions to the overall livability of our landscape were minimal. It occurred to us that there was something oddly poetic about a bath window view staring at the backside of a yew, but this was insufficient argument for leaving themin place. The Herbaceous Layer 173
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A top-down view in October shows the viburnums and bluestars at their autumn color peak. The asters have finished flowering by this time but their developing seed-heads are still standing, mostly obscured by the lax stems of the bluestars, We allow the herbaceous layer to stand through fall and winter. By late November, the bluestars have turned tawny and are more upright than they were in October (above). Their needlelike leaves begin dropping at this time and by spring they have contributed a significant amount of organic material to the ground layer. Along with leaves from the asters and shrubs, this material all but eliminates the need to spread mulch in this area. If we do need additional material, we use composted leaf mulch produced on site. We find the aster seed-heads quite beautiful (left), and take pleasure in knowing that they provide food for birds all winter long as well as new aster seedlings in spring to fill in any gaps in the herbaceous layer. —RD The Herbaceous Layer 177
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As this November image illustrates, the winter appearance isn’t exactly tidy but it is reasonably attractive, especially with snow cover, Because our herbaceous layer provides winter cover, this cardinal can safely forage on the ground below without fear of being spotted by a hawk. Attracted by the cover and food provide by our layered planting, this hermit thrush, photographed through the window (above and above left) has made regular visits in January for a few years now, and by February we can count on robins (opposite top right) and many other birds arriving to feast on viburnum berries. If we had wished to cut the bluestars back in fall, we would have needed clippers or shears. As the stems stand through winter their materials break down, and by March, they are fragile and brittle enough that they can easily be snapped off near the crowns with gloved hands, eliminating the need for bladed tools. The aster stems are also removed easily and quickly for composting at this time. —RD The Herbaceous Layer 179
. piedmont azalea ~ Ashland Hollow § Another fragrant native azalea, the (Rhododendron canescens), greets visitors to this Tare exe) ereli ice lolol a entry space at in Delaware.
# aa — 2 THE SHRUB LAYER etal’ Though not as diverse as the herbaceous layer, a | the shrub layer offers unique opportunities 4 NN / pp swe to add tothe beauty, diversity, and year-round a ; functionality of the garden. Along with trees, soba’ ” and accompanied by functional ground and her- * baceous layers, shrubs area gardener’s principal space-making materials. A oo Ms seer * Sweetshrub (Calycanthus floridus) is for more hours each day and more not a chance selection. All sweetone of the most distinctively scented spring days each year than most shrubs turn gold in autumn, and the native shrubs. For many weeks in sweetshrubs. It is also more upright color lasts quite a while as illustrated April and May, it fills the garden with and taller than many sweetshrubs and by this late-October image (above). the scent most people associate with the foliage is unusually glossy (top). The dense twigginess of sweetshrub fresh strawberries. These photos It is fertile and seedlings are true provides functional cover for birds and are of the horticultural selection to form, and ‘Michael Lindsey’ may it is frequently chosen as a nesting site. ‘Michael Lindsey’, which is fragrant actually represent a botanical type, The Shrub Layer 181
Taken in mid-May, these photos _ i give two different perspectiv on spaces in our garden de anchored by sh nthe arc ing sweep of shrubs nearest the _ chairs, Fothergilla xintermedia and sweet pepperbush (Clethra alnifolia) are repeated for v are interspersed to add to interest and functionality. The single white blooming shrub — (to the right in photo above) is coastal azalea (Rhododendron atlanticum) and it alone is capable of scenting this section of the garden with its sweet clovelike fragrance. Later in the season fragrance will be provided by the sweet pepperbush.
Native azaleas are easyto-grow, long-lived plants if provided with good drainage, slightly acid soil, and filtered sunlight. This mixed planting of pinxter azalea (Rhododendron periclymenoides) and piedmont azalea (R. canescens) has thrived in our garden for over 20 years with no pruning, fertilizing, or irrigation. —RD The Shrub Layer 183
ABOVE AND LEFT The colors of the highly fragrant Florida flame azalea (Rhododendron austrinum) vary from deep orange to orangeyellow ina mixed planting at Mt. Cuba Center in Delaware (above). Elsewhere at Mt. Cuba, a planting of pinkshell azalea (R. vaseyi) demonstrates that native azaleas can be used in relatively formal, refined designs (left). The groundcover is eastern foamflower (Tiarella cordifolia). Though this pinkshell azalea is not fragrant, its flowers are unequalled for their clarity of color. OPPOSITE Early May (top) and late-October (right) views of the same multilayered planting anchored by repeated fothergillas and river birches. Though the herbaceous layer has evolved and additional shrubs have been added, the fothergillas and birches have been growing together for over 20 years, depending almost entirely on rainfall. The main reason this works is that the fothergillas and birches were planted at modest size and at the same time. This isn't always possible, but when it is, it is ideal, allowing shrubs and trees to develop simultaneously the extensive root systems necessary to sustain them in times of drought. This is especially important when planting shrubs with surface-rooted, highly moisture-competitive trees such as river birch or American beech. The herbaceous layer also benefits from the opportunity to develop root systems before the ground is dominated by tree roots. Deeper-rooted trees such as blackgum (Nyssa sylvatica) and most of the oak species allow later planting of the shrub and herbaceous layers without risk of failure or the need for regular irrigation in dry times.
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white-throated sparrows enjoy the late-January cover afforded by -banded hairstreak takes nectar in mid-May. Viburnums are one of shrubs. Most have white flowers in flat-topped clusters and most produce colorful berries of great value to wildlife. from arrowwood useful groups of native rs <x ce a wi ue i > = c U ° Ww © f= mo) fothergillas planted with river birches. LEFT Ared viburnum (Viburnum dentatum) the larger and most CASEIN Sos SS \ ea . Rm, sjaswigenah a i’ ~~ SSNS Sek >. ‘<lmey oo se : acy = eo eee Sa Ne es a ony an a = ae SE ee Swe
Fothergilla and mapleleaf viburnum (Vibur- cozy and intimate in April even before most right) and by mid October it has become num acerifolium) provide the necessary of the garden has leafed out (top left). a virtual kaleidoscope of colors (above separation to make this seating area feel The viburnum blooms in late May (top left and right) rivaling the fothergillas. The Shrub Layer 187
Illustrating the opposite side of the same planting from page 187, these two images reveal the composition and seasonal dynamics of the herbaceous layer. Virginia bluebells bloom with the fothergillas in April (right) accompanied by the bright green new leaves of Allegheny pachysandra (Pachysandra procumbens) and bicolor barrenwort (Epimedium xversicolor ‘Sulphureum’), a hybrid with East Asian origins. In mid-November (below) the semi-evergreen foliage of the pachysandra and barrenworts provides rich green contrast to the shrubs. Applying Layers to the Home Garden
ABOVE Extensive shrub plantings at Longwood Gardens in Pennsylvania demonstrate how effective combined native shrubs can be in organizing spaces or edging walks. In this mid-July image, the low-growing selection of sweet pepperbush (Clethra alnifolia ‘Hummingbird’) transitions into a sweep of Virginia sweetspire (Itea virginica). LEFT Sweet pepperbush attracts a zebra swallowtail in July. The Shrub Layer 189
te opposite Always multistemmed, witch hazel (Hamamelis virginiana) has a reliable upright vase shape which makes it useful in a wide variety of settings in residential gardens. It is extremely long lived, continualiy sending up new stems and can be maintained at almost any desired height from 5 to 14 feet by removing the older taller stems. One of the most adaptable of all native shrubs, it can grow in deep shade or full sun, in deep organic soil, clay or thin rocky soil. It tolerates prolonged droughts or periodic inundation. Hamamelis virginiana blooms for a few weeks in October and November. For maximum flowering impact, select a seedling that drops its leaves before flowering. These images show the same 8-foot tall plant in mid-November (top left) and mid-February (far left). THIS PAGE Witch hazel creates a sense of enclosure around an outdoor shower area that doubles as a garden workspace. The clear yellow autumn color illustrated in this mid-October photograph is reliable and lasts for a couple of weeks (top). This particular plant was selected because it always drops its leaves before blooming as illustrated by this mid-November image (left). The two wine-colored shrubs flanking it are Korean spice viburnum (Viburnum carlesii). Chosen for its delightful spring fragrance and adaptability to the site conditions, this eastern Asian shrub does not naturalize in eastern North America. The last photo (above) shows the top-down view of the outdoor shower space in September. The Shrub Layer 191
RIGHT Though spicebush (Lindera benZoin) isacommon and wide-ranging native shrub, its clear yellow always brightens the autumn garden and its presence provides sustenance for spicebush swallowtails. Fragrant sumac (Rhus aromatica) is among the relatively small group of truly low-growing native shrubs whose rate of growth, adaptability, and durability make them suitable for ground cover use. A mass planting by Restaino Design beautifies and stabilizes a steep slope at The Flags in New York's Catskill region (right). When grownin sun, fragrant sumac colors vividly in autumn (above). 192 Applying Layers to the Home Garden
LEFT Black huckleberry (Gaylussacia baccata) is another low, colonizing shrub that makes a sturdy groundcover. This October image illustrates a planting onadryslopeina New York garden. Bottlebrush buckeye (Aesculus parviflora) is a large, highly adaptable spreading shrub that makes a dramatic addition to residential landscapes with adequate space (left). Its June-to-July flower spikes are followed by smooth red-brown chestnutlike seeds (above). Beautiful but not edible for humans, the seeds are valued by many small mammals and insects. The Shrub Layer 193
ABOVE Many experienced gardeners believe growing blueberries is for the birds. Highbush blueberry (Vaccinium corymbosum) grows best in full sun on moist soil with high organic content. It is worth growing as a well-formed shrub with vivid crimson autumn color even if birds manage to eat most of the berries. There are two ways to approach this. One is to cover the shrubs with netting as berries ripen. The alternative is to plant enough blueberry shrubs to produce sufficient berries for avian and human consumption. ABOVE RIGHT Redstem dogwood (Cornus sericea) can grow over 10 feet tall but can be maintained at much lower heights by cutting back nearly to the ground periodically. This image shows the cultivated variety ‘Cardinal’, which is not quite as brightly colored as its namesake but can be one of the more colorful elements in the winter landscape. Before cutting back any shrub, inspect it for signs of other life that might otherwise be overlooked. This February photo shows a praying mantis case ona dogwood stem (above). Postponing cutting back this shrub until the following year will allow the mantids to hatch in spring. Another option is to cut the stem with the case and 194 Applying Layers to the Home Garden position it near other vegetation somewhere else in the garden until hatching occurs. Assuming the mantid egg case is not eaten by woodpeckers, chickadees, or titmice during the winter, up to 200 tiny replicas of their parents will hatch and emerge sometime in May (above right). The entire clutch hatches within minutes and the young mantids move away from their siblings as fast as they can. Even when small, mantids are voracious predators and will attempt to eat anything they can grasp, including small flies, aphids, and each other. Many of the tiny hatchlings will fall victim to insect and bird predators and only a small percentage will live to become adults.
Alabama snow wreath (Neviusia alabamensis) happens to be rare inits native range through the southeastern states but it is an easily cultivated and beautifully useful addition to the shrub layer in gardens. It literally covers itself with starry white flowers in late April or early May (top and above), and is pretty enough that for years we've been using it as a cut flower (above right). Its greatest value to usis asa deer-proof screening shrub. Though deciduous, this running species produces a dense profusion of red-brown stems that form nearly opaque mass that stands through winter. It is easily increased by division in late winter or early spring. —RD The Shrub Layer 195
Oakleaf hydrangea (Hydrangea quercifolia) occurs in woodland habitats in the southeastern states from Tennessee to North Carolina and south to Louisiana and Florida, typically on alkaline soils. In recent decades, interest in indigenous North American species has propelled it froma relatively obscure “native” to a popu196 Applying Layers to the Home Garden lar shrub widely valued for its beauty, adaptability, and utility. Although lower-growing selections are increasingly available, the typical form can grow over 10 feet tall. This would be too large for many residential gardens; however, oakleaf hydrangea tolerates repeated pruning or even occasional cutting back to the ground. It is a superb example of a native shrub that is suited to a wide range of design styles and purposes. It can be used as a Space-defining mass (above), or as these two examples at Longwood Gardens demonstrate, a backdrop for a casual space (top right) or a bold-textured presence in a highly formal design (bottom right).